1. Field of the Invention
This invention relates to conduit formation and more particularly to a tool which provides phase ring shapes and dimensions suitable for joining with standard sized sleeves.
2. Description of the Prior Art
Large dynamoelectric machines such as turbine generators often include hollow phase rings and arcuate extensions thereto which connect external main bushings to various phase winding terminating portions. The phase rings are usually hollow to accommodate internal coolant flow therethrough for the removal therefrom of electrical heating. The phase rings and arcuate extensions thereof are commonly square or rectangular cross-section hollow copper conduit. Typically, a number of bends must be formed in the phase rings and arcuate extensions to avoid interference with other generator components. It has been found advantageous to assemble phase ring components rather than form a phase ring of complex shape from a single straight piece of copper conduit.
Joining separate phase ring components into a phase ring assembly has, heretofore, been accomplished by brazing the connecting joints. Such connection joints are commonly of the scarf or miter type. A disadvantage of such scarf and miter joints is that they cannot be routinely inspected through their thickness by non-destructive ultrasonic testing means. Additionally, ultrasonic testing is not feasible in the axial direction along the joint since the portions of the phase ring components adjacent the joint are typically curved rather than straight and are thus not susceptible to ultrasonic analysis of the brazed joint. Joint quality of such a brazed joint is usually quantified by estimating a percent bond. Such estimate can be highly speculative and vary substantially from inspector to inspector.
U.S. Pat. No. 1,725,592, which was patented Aug. 20, 1929, illustrates a method of forming a square crosssectional conduit by using a former such as a vise on the exterior of the conduit and a mandrel on the interior of the conduit. The one-piece mandrel 2 illustrated in the aforementioned patent can be difficult to insert and extract subsequent to the forming operation. Use of the method disclosed in the aforementioned patent would be highly disadvantageous for use on retrofitting or repairing phase rings in an assembled dynamoelectric machine such as a generator. Space limitations in such machines require compact driving mechanisms for supplying the exterior and interior force necessary to properly form the conduit or, in the case of the prior art patent, dry cell container. As such, the illustrated apparatus could be utilized to form square conduit ends in such manner as to cause them to be suitable for joining with a sleeved joint only in work areas providing substantial access to the work pieces and drive equipment.
Primary problems associated with prior art phase ring joints and the tools to make those joints include the difficulties encountered in performing ultrasonic inspection tests thereon, tool complexity, and the large space requirements for operating the tools.